a person who never says much to anyone, who rarely speaks, and if so only in brief bursts of monosyllabic meter.

Churchgoer 1: Hey, Marty, how's your family, Merry Christmas, it's so great to see you, you look well, God bless us all at this special time of year, and can you believe this weather, just spectacular, wouldn't you say?
Marty: shuR thanKs, Mrry krisMas *leaves*
Churchgoer 2: That Marty's pretty much a tightlips, isn't he.